Field Plate Isolation Structure for High-Voltage Drift Regions
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Solution Overview
Problem
High voltage transistor devices face issues with electric field accumulation at the edge of the field plate, leading to substrate damage and reduced performance due to increased resistance and reduced lateral distance of the drift region.
Innovation Solution
Incorporating a buried isolation structure within the drift region, separated from the field plate by an etch stop layer, to mitigate electric field accumulation and maintain current flow, thereby enhancing device stability and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the lateral distance of the drift region is reduced to increase device density, then device integration is improved, but electric field accumulation occurs at the field plate edge causing substrate damage and increased resistance
Solution Approach 1:
A buried isolation structure is introduced as an intermediary element positioned between the field plate and the drift region. This isolation structure intercepts and redistributes the electric field lines, preventing field accumulation at the field plate edge that would otherwise cause substrate damage. The isolation structure acts as a mediator that enables reduced drift region lateral distance while maintaining substrate protection.
Solution Approach 2:
The solution moves from a two-dimensional planar configuration to a three-dimensional structure by introducing a buried isolation structure that extends vertically into the substrate. This vertical dimension allows the isolation structure to interact with electric field lines in a new spatial configuration, enabling field redistribution without increasing the lateral footprint of the device.
2Productivity
If the lateral distance of the drift region is reduced to increase device density, then device integration is improved, but resistance in the drift region increases
Solution Approach 1:
The buried isolation structure serves as a mediator that modifies the electric field distribution in the drift region. By positioning the isolation structure beneath the field plate, it creates additional field paths that reduce the effective electric field stress on the drift region, allowing for reduced lateral distance without compromising resistance characteristics.
3Reliability
If a field plate is placed over the drift region to control electric fields, then breakdown voltage is improved, but electric field accumulation occurs at the field plate edge
Solution Approach 1:
The buried isolation structure is positioned as an intermediary between the field plate and the drift region, specifically designed to intercept electric field lines that would otherwise accumulate at the field plate edge. This mediator structure redistributes the field lines vertically and laterally, eliminating the harmful field accumulation while preserving the field plate's breakdown voltage enhancement function.
Solution Approach 2:
The invention converts the potentially harmful electric field accumulation at the field plate edge into a beneficial distribution pattern. By introducing the buried isolation structure, the electric field that would have been concentrated and damaging is instead redistributed in a controlled manner, with the isolation structure itself becoming part of the field management system that enhances overall device reliability.
Data Source
AI summary
An integrated chip includes a gate structure overlying a substrate between a source region and a drain region. A field plate is disposed within a first dielectric layer overlying the substrate. The field plate is laterally offset from the gate structure by a non-zero distance in a direction towards the drain region. An isolation structure is disposed within the substrate. The field plate directly overlies at least a portion of the isolation structure.